1. Field of the Invention
The present invention relates to a carbon rupture disk element and assembly, and more particularly, to an improved replaceable carbon rupture disk element and a holder-element assembly.
2. Description of the Prior Art
A great variety of rupture disks for preventing excessive fluid pressure in vessels or systems have been developed and used hereto fore. The rupture disks function to relieve fluid pressure by rupturing when a predetermined pressure is exerted thereon, and they have been formed of various materials including metals, plastics and carbon, e.g., graphite and baked carbon.
Graphite rupture disks which have been impregnated with resins to make them gas tight have been found to be advantageous in that they are economical to produce, have excellent chemical corrosion resistance, do not creep and fatigue as a result of pressure variations and reliably fail at their predetermined rupture pressure regardless of temperature variations.
The carbon rupture disks utilized heretofore have generally been of two types. The first and most common is the monoblock type comprised of a carbon disk having a central bore machined therein which extends from one side of the disk towards the other side thereof. The depth of the bore is such that the carbon material remaining between the bottom of the bore and the other side of the disk is of a thickness and strength whereby it ruptures at a predetermined desired rupture pressure. The disk is of a large size so that it can be bolted directly between pipe flanges or the like, and when the predetermined rupture pressure is reached, the central portion of the disk between the bottom of the bore and the other side of the disk blows out and relieves pressure therethrough.
The second type of carbon rupture disk unit utilized heretofore is an improvement over the monoblock disk in that it includes a replaceable carbon element. That is, the unit is comprised of an assembly of a carbon rupture disk element positioned between annular holders formed of carbon or other material. The holder-rupture disk element unit is sealingly clamped between pipe flanges or the like whereby the rupture disk element is in turn sealingly clamped between the holders. Upon rupture, the rupture disk element can be replaced without replacing the holders.
While the above described heretofore utilized carbon rupture disks and assemblies have achieved varying degrees of success, they suffer from the disadvantages that they are sensitive to compressive forces and they are directional, i.e., they rupture at the predetermined rupture pressure in only one direction. More specifically, the rupture pressures of prior carbon rupture disks are changed when excessive compressive forces are exerted on the disks as a result of being clamped between holders and/or pipe flanges. That is, when a carbon rupture disk is subjected to compression forces to assure a pressurized fluid seal, stresses are introduced into the brittle carbon material which change the pressure at which the disk ruptures.
The directional rupture aspect of prior carbon rupture disks requires that such a disk be installed between holders and/or pipe flanges with a particular side of the disk facing the fluid pressure. If the rupture disk is inadvertently installed upside down, the fluid pressure at which the disk ruptures is changed which can bring about a premature rupture or a dangerous overpressure condition.
Thus, there is a need for an improved carbon rupture disk element and holder-element assembly whereby the carbon rupture disk element can be subjected to excessive compressive forces without changing the rupture pressure of the disk, and whereby the carbon rupture disk element can be installed with either side thereof facing the inlet fluid pressure without affecting the rupture pressure.